1. Field of the Invention
The present invention relates to a distance measuring apparatus and a focusing device.
2. Description of Prior Arts
Conventionally, the cameras having a distance measuring apparatus for taking a still image as a photographic subject conducts exposure control of processing for focusing or the like, depending not upon a presence or absence of luminance change in a subject due to movement of the subject in distance measurement but on a result of distance measurement at that time.
Also, the distance measuring apparatuses employed in the cameras or the like include those for detecting a moving state of a subject as a photographic object. These operate to measure distances in plurality of times at a predetermined time interval to thereby detect subject movement based on a result of distance measurement. Furthermore, complicate exposure control operation is made in compliance with a moving subject.
However, in the former case, there encounters a problem that an accurate distance to a subject is not to be obtained where there is state change in the subject as an object due, for example, to movement of the subject during distance measurement or change in subject luminance or approach of other object to a vicinity of the subject. Also, there is another problem that accurate focusing is impossible to perform by utilizing those measurement results.
The latter requires repeated operations of measurements, resulting in a problem that distance measurement takes long time with increased power consumption. Furthermore, complicated processing is required, i.e. distance measurement is repeatedly made to compare between the results thereof.
A distance measuring apparatus of the present invention comprising: a monitor element for generating an output depending on an intensity of light of an object; a charge-storage type light receiving element formed by a plurality of pixels for receiving the light of the object; a control circuit for controlling storage operation of the charge-storage type light receiving element depending on the output of the monitor element; a distance detecting circuit for detecting a distance to the object by a photoelectric output of the charge-storage type light receiving element; and a detection-signal output circuit for outputting a detection signal when there is change in output of the monitor element during storage operation of the charge-storage type light receiving element. Accordingly, the utilization of a detection signal makes it possible to confirm on a state that a distance to an object is not correctly obtained. Also, the structure can be simplified because the output of the monitor element required for controlling storage operation of the charge-storage type light-receiving element is used in status change determination of the object during distance measurement operation.
If the detection signal is to prohibit the storage operation or to issue an alarm or to determine that the object has moved, it is possible to prevent from outputting a distance measurement result low in reliability or to recognize a user that a distance measurement result is low in reliability. Also, it is possible to make unnecessary repeated distance measurement operations when detecting a movement of the object. Accordingly, moving object detection can be made in a brief time, reducing power consumption. Also, in the conventional, object movement could not have been detected during distance measurement operation because of detection of subject movement from a distance measurement result. However, in the present invention, subject movement can be detected even during distance measuring operation thus reducing the detection time and power consumption. Also, complicate processing of performing repeated distance measuring operations and comparison of the results thereof can be made unnecessary.
Included are the distance measuring apparatus and focusing section for performing focusing of a lens based on a detected distance to the object by the distance measuring apparatus. Accordingly, a similar effect to the above is provided. Further, the accuracy of focusing is improved because of prevention from focusing based on a distance measuring result low in reliability and of recognizing a user that focusing is low in reliability.